Centrifugal unloader



June 30, 1925. .7 1,543,686"- s. B. REDFIELD CENTRIFUGAL unnowmi Filedlay'2, 1923 5 Elects-Elect 1 HHS ATTOR Y Julie 30, 1925'.

5. B. REDFIELD' CENTRIFUGAL UNLdADER y 2, 1923 3 Sheets-Sheet 2 Filed Ma INVENTOR nowanaflafwzd.

H I 5 ATTORN June 30, 1925. I 1,543,680 j S. B. REDIFIELD I CENTRIFUGALURLOADER Filedlay 2, 1923 3 Sheets-Sheet 5 HIS ATTOR Y drawings.

Patented June 30, 1925.

UNITED STATES PATENT oFFloa.

SNOWDEN B. BEDFIELD, OF EASTO'N, PENNSYLVANIA, ASSIGNOR TO INGERSOLLRAND COMPANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

CENTRIFUGAL UNLOADER.

Application filed Kay 2,

To all whom it may concern."

Bef'it known that l, SNOWDEN B. RED- FIELD, a citizen of the UnitedStates, a resident of Easton, county of Northampton, and State ofPennsylvania, have invented a certain Centrifugal Unloader, of which thefollowing is a specification, accompanied by This invention relates tocompressor unloaders, but more particularly to an unloader for relievingthe fluid compression load during the period of starting. The objects ofthis invention are to enable a compressor unloader to be controlled bythe speed of the driving element of the compressor.

Further objects of the invention will hereinafter appear, and theinvention is shown in the accompanying drawings in one of its preferredforms, in Which Figure l is a side elevational view partly in 'sectionof a compressor unit with my invention applied thereto,

Fi ure 2 is a view similar to Figure 1 showing the parts in runningposition,

Figure 3 is a diagrammatic view, partially in longitudinal section of anunloader with a' modified form of my invention applied thereto, and vFigure 4 is an enlarged detail view partially in vertical section of thechoking needle valve,

Referring to the drawings, the compressor comprises the cylinder A, inwhich a piston (not shown) reciprocates. Thedriving element forthecompressor piston comprises the crank shaft B, mounted in the frame Bto which the connecting rod C is attached for moving the cross head D.The fly wheel E is secured in any suitable manner tothe crank shaft B.

The unloader F is connected to the discharge line G between thecompressor and the usual receiver H. The unloader comprises a valvecasing J having a main valve chamber K separated from the outlet L by apartition 0 on which the main check valve P is adapted to be seated forcontrollin the discharge from the casing. The chec valve P is providedwith a spring Q bearing on the valve and held b a cap R, which cap alsoforms a valve gui e. The pressure in the receiver tank H normally holdsthe main check valve P to its seat, when the "compressor is idle.-

1923. Serial No. 636,080.

the communication between the main valve chamber K and anatmosp'hericrelief port V, conveniently located on the side of theextension W of the main casing J, in which the reliefvalve U operates,The relief valve U. is preferably carried by a piston X and has limitedlongitudinal movement relatively to the piston, being urged outwardlyfrom the piston X by a comparatively heav coil spring Y, in the valvesocket 'Z, of su ficient strength to resist the full line pressure inthe main valve chamber K and revent the relief valve from openingagainst the spring due to said pressure, when the Valve is held to itsseat by the combined spring pressure and fluid pressure behind t episton X. The movement of the relief valve is limited by a pin a passingthrough the transverse aperture 6 in the valve, and secured at each endof the valve piston X, The piston X is of the difi'erential type,provided with an enlarged head 0 forming a pressure area materiallygreater than the opposed pressure area on the face of the relief valve Uand pressure behind the piston head 0 will force the relief valve U toits seat T with sufficient force to compress the spring Y and also holdthe piston head 0' firmly against theseat a? in the extension W, so thatleakage past the piston from behind the piston head is prevented. Therelative longitudinal movement provided be- .,tween the relief valve Uand the piston X, enables both the valve and the piston to be tightlyseated on their seats T and d respectively.

A projection or stop 6 on the piston X is adapted to bear upon anadjusting screw 2 in the cap g, by means of which the initial startingposition of the piston X and relief valve U may be adjusted. A bypassitto operate for loading. Adjustment of the screw f behind the piston Xdetermines the pressure'to which the side discharge to atmospherethrough the port or vent V will be built up by the relief valve U by thetime the compressor has reached full speed. This adjusting screw fshould preferably be set at a point to produce just enoug throttling atthe relief valve U to move the piston inwardly and close the reliefvalve U when the choking needle valve k is set well towards its seat inthe port 9'. Throttling, due to the slightl open relief valve U needs:not be considera 'le, but should be at least a pound or two, in orderto start building up an initial pressure behind the piston X to beginmoving the piston X and relief ,valve U towards the seat T to close theoutlet to atmosphere through the port V. r

A valve casing o in this instance supported by a'column p, is providedwith an a-tmosp eric vent g. A plunger valve 1' is adapted to be movedlongitudinall in the bore 8 of the valve casing 0. A coi spring t, theten- .sion of which may be adjusted by the set screw'u, bears againstone end of the plunger ,valve 1'. The bore 8 of the valve casing 0 is incommunication with theextension W of the main valve casing J, rearwardlyof the piston X, by means of a pipe or tube '0. It

will readily be understood that when the compressor is idle, the spacein the rear of the piston X in the extension W of the main valve casing,will be open to atmosphere through the pipe or tube 0, the bore a of thevalve casing o and the atmospheric vent q. By moving the plunger valve rto the left, as shown in Figure 2, the passage of fluid to atmospherefrom behind the piston X will be revented.

frame 'w is secured to the crank shaft B of the compressor by anysuitable means, as screws 'w'-. A plurality of weighted bell cranklevers ware mount d on the frame 10. Thesmaller unweighted nds w of thelevers a: are in contact with a collar 3 which is v adapted to be movedlongitudinally on the shown in spindle 2. 1s threaded into the crankshaft B. Theextension 3 of the collar 3 is adapted to bear against oneend of the plunger 1'.

Assuming that the compressor is starting, the'imtial osition of the artswill be as lgure 1, and fluid pressure will be forced out to atmospherethrough the vent V in the extension W of the main valve casing, and aportion thereof will as from the main valvechamber K, throu the passageh, ort j, pipe or tube-'0, t ough the bore 8 o the valve casing O andout through the atmospheric vent g. As soon as sufficient speed has beenattained, centrifugal force will cause the Weighted bell crank levers asto fly outwardly as shown in Figure 2, and by means of the collar 3 andextension y,

The spindle z in this instance,v

Pressure through the vent V. Sufficient pressure will then be built upin the valve chamber Kto overcome the receiver pressure and unseat thevalve P in order to force the fluid pressure into the receiver H. 1

As the compressor stops, the above described operation will be reversed.The

Weighted levers m will tend to assume their normal or inward position,and thereby permit the coil spring t to move the plunger valve 1- to theright, and open the passage of fluid from the extension W of the mainvalve casing in rear of the piston X to atmosphere through. the port 9in the valve casing 0. Pressure fluid Will be allowed to pass out of thetube '0 and vent q faster than it can enter the space back of the pistonhead 0 through choking needle valve is. This will reduce the fluidpressure back of the piston head 0 to such a point that the pressure inthe main chamber K will unseat the relief valve U, thereby allowingfluid to pass out through the atmospheric vent V. Load will thus bethrown ofl the compressor and enable the compressor piston to restartunloaded.

In the modification shown in Figures 3 and 4, the same principleheretofore described is applied to an unloader in which the /passage 72.in the extension W of the main valve casing is omitted. In thisinstance, the pipe or tube 2 is connected to the main valve chamber Kand is in communication with the valve casing 0', which is supported inany suitable manner, as by the angle bar 1). The bore 8 in the valvecasing o communicates 'with the smaller bore t which is in communicationwith the pipe or tube '0'. The opposite end of the pipe or tube '0' isconnected to the extension W of the main valve casing rearwardly of thepiston X. A ball check valveu urged against its seat It by the coilsprin u con-' trols the passage of pressure fluid, om the main valvechamber K to the rear of the piston X. A ball check valve :12 in thebore 2 of the valve casing o' is spaced from the all valve u by thespacer pin 2' and controls the atmospheric vent 3.

A plate 4 secured in any suitable manner to the end of the compressorshaft 5 as b means of the screws 6, is provided with the lugs 7. Theweighted bell crank levers 8 are pivotally mounted on the ln 7, and areadapted to bear against the end 9 of the lunger 10 for moving theplunger inwar y, in the casing 0'. The inner end 11 of the plunger 10 isadapted to'bear against and seat the ball -valve A coil spring 12 issecured at its ends to the ins 13 in the levers 8, and serves to hol thelevers 8 Assuming that the compressor is starting, I

the wei hted levers will e caused to move outwargly b centrifugal force,and thereby move the p unger 10 inwardly to seat the ball valve :12. Bymeans of the spacer z,

1 the ball valve to W111 be unseated' thereby permitting fluid pressureto flow from the main valve chamber K" through the pipe or tube 2int0the bore ,9 of the valve casingo,

\ through the bore the ba 1 valve u and b means 0 the spacer the mainvalve casing.

t and thence through the pipe or tube 0; to The iston X will thereuponbe forced in-v war y, forced to its seat T, thereby closing theatmospheric vent V in the extension W" of On stoppin the levers 8 willtend to move together by t e action of the coil spring 12, therebpermitting the coil sprin u to seat pin 2', unseat the b valve 0:.Pressure fluid may then pass from behind the piston K through the pipeor tube '0 into the bore t of the valve casing o and thence to atpassingchoking p s g V rectly from the compressor an controlling.

"a centrifugally oper- 5 valve with atm v ing adapted .to control themospherethrough the vent 3.

As shown in Figure 4, I provide a set screw 14 preferably threaded'mtothe main valve chamber K forming a choking needle valve, which controlsthe amount of fluid I out of the main valve chamber. K into the pipe ortube 2. Byregulating the needle valve, the closing the relief valve Umay be delay or has- 1. A- centrifugal compressor unloader a 'rehef'valve in. the dischai' e line exposed on both ends to ressure a vent toatmosphere, able pilot valve, and a conduit connecting one face of thereliefvalve through the pilot here, said pilot valve bethe rear of thepiston X;

and the relief valve U will be.

oint of opening of said -ebnduit to atmosphere whereby the relief valveis arranged to be actuated.

2. A centrifugal compressor unloader comprising a. relief valve in thedischarge line exposed on both ends to pressure directly from thecompressor and controlling a vent to atmosphere, a centrifugallyoperable pilot valve, and a conduit connecting one face of the reliefvalve through the pilot valve with atmosphere, and adjustable meansrestricting the flow of air to and from one side of the relief valve.

3. A centrifugal compressor unloader, comprising an unloader mechanismadapted to be connected in the discharge line 'of the com ressor, saidunloader mechanism comprising a main discharge valve casin provided witha discharge valve cham r, "a main discharge valve controlling the outletfrom the casing, an extension connected to said casing, a piston in theextension, a relief valve havm limited movement in the piston, adapte tocontrol an atmospheric vent in the extension, a connection between thedischarge valve chamber and the space in rear of the piston, a chokingvalve controlling the tion, centrifugal means for controlling the oeration of the unloader mechanism operatively connected to the drivinelement of 'the compressor comprising a ame, a plurality of weightedbell crank levers pivotally. mounted on the frame, a spindle ured to theframe acollar provid with n extension slida ly mounted on the spindle,the movement of the collar on the s ing controlled by one end of the 11crank levers, a plunger valve casing-in communication with the extensionof the main valve casing rearwardly of the piston, a' plunger valve vinthe plunger valve casing-adapted to be moved in one direction by saidextension for controlling an atmospheric vent therein, a spring in theplunger valve casing opposing the movement 0 theval-ve in 'one drection, whereby" the load is thrown on and oi the compressor inaccordance with its speed. v In testimony whereof I have signed thisspecification a i. SNOWDEN B. REDFIELD.

indle be-

